Great Lakes see decrease in number of blood sucking sea lampreys

The Great Lakes Fishery Commission says the levels of the eel-like blood suckers who prey on fish in the Great Lakes are trending downward.

The number of sea lampreys is at a 30-year low in Lake Huron, and at a 20-year low in Lake Michigan. Their population is also decreasing in Lake Erie, Lake Superior and Lake Ontario.

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Barb Zielinski, a biologist and sea lamprey specialist at the University of Windsor said this is great news for the Great Lakes.

"It's goodfor the ecosystem, it's good for the fisheries," Zielinski said in an interview with CBC News. "A lot of the efforts on conservation can latch on, because these fish you're trying to establish are not being limited by the sea lamprey."

Sea lampreys, with their rows of razor sharp teeth prey on sturgeon, trout, salmon and whitefish. One lamprey alone can kill up to 18 kilograms of fish during its parasitic stage.

The predators feed by latching onto its prey, filing a hole through the fish's scales. Lampreys don't have a natural predator in the Great Lakes, so they feast on vulnerable fish.

The invasive species first entered the Great Lakes in 1939.

Before programs to control the sea lamprey population began in 1954, they were responsible for killing an estimated 47millionkilograms of fish each year. Today, that number is down to 4.5 millionkilograms, the commission reports.

Zielinski said it's important to reduce the sea lamprey population before any effective conservation can happen.

"Lamprey prey on fish where they're already stressed because of a loss of habitat. So there's a lot of habitat restoration going on around the Great Lakes," Zielinski said.

"Part of that is giving them a healthy environment to return [to], that's not only their physical environment, but also giving them a habitat without predators."